The present invention relates to a hydraulic valve device for a hydraulic circuit suitable for controlling clutches, brakes and other similar mechanisms, incorporating a cylinder, a piston mounted to slide in this cylinder and defining in it a chamber of variable volume connected to the hydraulic circuit, and a tank connected to the chamber by a passage having a non-return valve.
This tank is intended for replenishing the hydraulic circuit during operational conditions. The purpose of the non-return valve is to isolate the chamber from the tank when the piston is displaced in the direction of pressurization of the circuit and to ensure, in the position of rest, communication between the chamber and the tank.
However, in the return movement of the piston in which the chamber is depressurized, it is expedient to prevent liquid, drawn from the tank towards the chamber and prevented from returning to it during pressurization of the said chamber, from overloading the hydraulic circuit. Consequently, the non-return valve generally incorporates a stem which interacts in a pivoting manner with the piston, so as to provide a permanent two-way communication between the tank and the chamber when the piston is at rest or in a position adjacent to the position of rest.